Print Psychrometrics

The section describes what is printed when Print Psychrometrics is checked in the Print Load Calculations dialog box.

Print Load Calculation Dialog Box

Load Calculations--Print Load Calculations.Print Psychrometrics

Psychrometrics

An individual Psychrometrics table is printed for each zone in the project. If the whole building is selected to be printed in the Zone or Room to Print field, then a table for every zone is printed. If specific zones are selected, then only the selected zones are printed.

The important values that are calculated in this table are Coil Dew Point, Reheat, and Humidification. All the other rows are values you input using the various load calculations commands.

Load Calculations--Print Load Calculations.Print Psychrometrics.report

Calculation Month: The month with the highest humidity that is used in the calculation.

Calculation Hour: It is assumed that the highest humidity happens at 4pm.

Outside Air

Airflow: The total ventilation airflow for the zone. Includes additional air to account for any air lost due to Return Duct Leakage set in the Zone List command.

Dry Bulb Temperature: Set using the OSA High Dry field for the Calculation Month in the Project Info command.

Wet Bulb Temperature: Set using the OSA High Wet field for the Calculation Month in the Project Info command.

Humidity Ratio: Calculated based upon the Dry Bulb Temperature and Wet Bulb Temperature.

Total Load: The sum of the Sensible Load and Latent Load.

Sensible Load: The sensible ventilation load.

Latent Load: The latent ventilation load.

Return Air at Diffusers

Airflow: The airflow at the return diffusers.

Dry Bulb Temperature: The return air temperature at the diffusers. Set using the Cooling Temperature field in the Zone List command.

Wet Bulb Temperature: The return air wet bulb temperature at the diffusers. Calculated using the Cooling Temperature and Relative Humidity fields in the Zone List command.

Humidity Ratio: The return air humidity ratio at the diffusers. Calculated using the Cooling Temperature and Relative Humidity fields in the Zone List command.

Plenum Load

The plenum row is included if the Plenum Return field is checked in the Zone List command.

Dry Bulb Temperature: The temperature gain in the airflow based upon the Total Load.

Total Load: The load in the plenum. See the Print Cooling Detail section for more information.

Sensible Load: There is no latent load, so Total Load and Sensible Load are the same.

Return Duct Leakage

Airflow: The volume of air leaked out of the return ducts. It is replaced with outside air. Set using the Return Duct Air Leakage field in the Zone List command.

Return Duct Temperature Gain

Dry Bulb Temperature: The change in temperature in the air in the return ducts. Set using the Return Duct Temperature Gain field in the Zone List command.

Total Load: The temperature gain converted to Btu/h based upon the return duct airflow.

Sensible Load: There is no latent load, so Total Load and Sensible Load are the same.

Return Air at Apparatus

Airflow: The return airflow at the piece of mechanical equipment. Includes any loss due to Return Duct Leakage set in the Zone List command.

Dry Bulb Temperature: The return air temperature at the mechanical equipment. Equal to Return Air at Diffusers Dry Bulb Temperature plus Plenum Load Dry Bulb Temperature plus Return Duct Temperature Gain Dry Bulb Temperature.

Wet Bulb Temperature: The return air wet bulb temperature based upon the calculated Dry Bulb Temperature and the Return Air at Diffusers Humidity Ratio.

Humidity Ratio: The dry bulb temperature change does not affect the amount of moisture in the return air. This value is the same as Return Air at Diffusers Humidity Ratio.

Mixed Air

Airflow: The sum of the Outdoor Air Airflow and Return Air at Apparatus Airflow.

Dry Bulb Temperature: The average of the Outdoor Air Dry Bulb Temperature and Return Air at Apparatus Dry Bulb Temperature, weighted by their relative airflow volumes.

Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.

Humidity Ratio: The average of the Outdoor Air Humidity Ratio and Return Air at Apparatus Humidity Ratio, weighted by their relative airflow volumes.

Fan (Blow Through)

This row is included if the Fan Position field is set to Blow Through in the Zone List command.

The Fan Brake Horsepower set in the Zone List command is displayed in the row label.

Dry Bulb Temperature: The rise in temperature based upon the Mixed Air Airflow and Total Load.

Total Load: The load from the fan based upon the Fan Brake Horsepower set in the Zone List command.

Sensible Load: There is no latent load, so Total Load and Sensible Load are the same.

Motor (In Airstream)

This row is included if the Motor Position field is set to In Airstream and Fan Position field is set to Blow Through in the Zone List command.

The Motor Efficiency set in the Zone List command is displayed in the row label.

Dry Bulb Temperature: The rise in temperature based upon the Motor Efficiency and Fan Brake Horsepower set in the Zone List command.

Total Load: The temperature gain converted to Btu/h based upon the Mixed Air Airflow.

Sensible Load: There is no latent load, so Total Load and Sensible Load are the same.

Motor (Out of Airstream)

This row is included if the Motor Position field is set to Out of Airstream and Fan Position field is set to Blow Through in the Zone List command.

Coil Entering Air

This row is included if the Fan Position field is set to Blow Through in the Zone List command.

Airflow: The same value as the Mixed Air Airflow.

Dry Bulb Temperature: The air temperature right before it enters the coil. Equal to Mixed Air Dry Bulb Temperature plus Fan Dry Bulb Temperature plus Motor Dry Bulb Temperature.

Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.

Humidity Ratio: The same value as the Mixed Air Humidity Ratio.

Coil Dew Point

Airflow: The volume of air that passes over the coil. Equal to Mixed Air Airflow minus Coil Bypass Air Airflow.

Dry Bulb Temperature: The dew point temperature that corresponds to the Humidity Ratio.

Wet Bulb Temperature: The same value as the Dry Bulb Temperature.

Humidity Ratio: The humidity ratio necessary to achieve the design conditions for the rooms in the zone. Calculated based upon the Coil Dew Point Airflow, Coil Bypass Air values, and Supply Air at Diffusers values.

Coil Bypass Air

Airflow: The volume of air that is not conditioned by the coil. Equal to Mixed Air Airflow multiplied by Coil Bypass Factor set in the Zone List command.

Dry Bulb Temperature: The temperature is the same as the Mixed Air Dry Bulb Temperature or Coil Entering Air Dry Bulb Temperature, depending upon the Fan Position setting.

Wet Bulb Temperature: The wet bulb temperature is the same as the Mixed Air Wet Bulb Temperature or Coil Entering Air Wet Bulb Temperature, depending upon the Fan Position setting.

Humidity Ratio: The humidity ratio is the same as the Mixed Air Humidity Ratio or Coil Entering Air Humidity Ratio, depending upon the Fan Position setting.

Coil Leaving Air

Airflow: The volume of air that leaves the coil. Equal to Mixed Air Airflow.

Dry Bulb Temperature: The average of the Coil Dew Point Dry Bulb Temperature and Coil Bypass Air Dry Bulb Temperature, weighted by their relative airflow volumes.

Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.

Humidity Ratio: The average of the Coil Dew Point Humidity Ratio and Coil Bypass Air Humidity Ratio, weighted by their relative airflow volumes.

System Load

Total Load: The total system cooling load for the zone.

Sensible Load: The sensible system cooling load for the zone.

Latent Load: The latent system cooling load for the zone.

Reheat

Dry Bulb Temperature: Equal to the AHU and Coil Settings, Cooling Temperature field set in the Zone List command minus the Coil Leaving Air Dry Bulb Temperature.

Humidification

Humidity Ratio: Equal to Supply Air at Diffusers Humidity Ratio minus Coil Leaving Air Humidity Ratio.

Fan (Draw Through)

This row is included if the Fan Position field is set to Draw Through in the Zone List command.

The Fan Brake Horsepower set in the Zone List command is displayed in the row label.

Dry Bulb Temperature: The rise in temperature based upon the Coil Leaving Air Airflow and Total Load.

Total Load: The load from the fan based upon the Fan Brake Horsepower set in the Zone List command.

Sensible Load: There is no latent load, so Total Load and Sensible Load are the same.

Motor (In Airstream)

This row is included if the Motor Position field is set to In Airstream and Fan Position field is set to Draw Through in the Zone List command.

The Motor Efficiency set in the Zone List command is displayed in the row label.

Dry Bulb Temperature: The rise in temperature based upon the Motor Efficiency and Fan Brake Horsepower set in the Zone List command.

Total Load: The temperature gain converted to Btu/h based upon the Coil Leaving Air Airflow.

Sensible Load: There is no latent load, so Total Load and Sensible Load are the same.

Motor (Out of Airstream)

This row is included if the Motor Position field is set to Out of Airstream and Fan Position field is set to Draw Through in the Zone List command.

Supply Duct Leakage

Airflow: The volume of air leaked out of the supply ducts. Set using the Supply Duct Air Leakage field in the Zone List command.

Supply Duct Temperature Gain

Dry Bulb Temperature: The change in temperature in the air in the return ducts. Set using the Return Duct Temperature Gain field in the Zone List command.

Total Load: The temperature gain converted to Btu/h based upon the return duct airflow.

Sensible Load: There is no latent load, so Total Load and Sensible Load are the same.

Supply Air at Diffusers

Airflow: The supply airflow required to condition the zone. This value is the same as the Required Supply CFM column in the Supply Air Requirements table. See the Print Supply Air Requirements section for more information.

Dry Bulb Temperature: Set using the AHU and Coil Settings, Cooling Temperature field in the Zone List command.

Wet Bulb Temperature: Calculated based upon the Dry Bulb Temperature and Humidity Ratio.

Humidity Ratio: The humidity ratio is the same as the Coil Leaving Air Humidity Ratio.

Room Load

Humidity Ratio: Calculated based upon the Latent Load and Supply Air at Diffusers Airflow.

Total Load: The total room cooling load for the zone.

Sensible Load: The sensible room cooling load for the zone.

Latent Load: The latent system room load for the zone.

Final Room Conditions

Dry Bulb Temperature: Set using the Indoor Air Defaults, Cooling Temperature field in the Zone List command.

Wet Bulb Temperature: Calculated based upon Indoor Air Defaults, Cooling Temperature and Indoor Air Defaults, Relative Humidity fields in the Zone List command.

Humidity Ratio: Calculated based upon Indoor Air Defaults, Cooling Temperature and Indoor Air Defaults, Relative Humidity fields in the Zone List command.


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